如何使用array_walk在PHP中对三维数组进行排序？

Question

我有以下数组：

Array
(
    [1] => Array
        (
            [0] => Array
                (
                    [class] => Advanced Hip Hop Ages 10+
                    [session] => 0
                    [start] => 1436902200
                    [end] => 1436905800
                    [capacity] => 
                    [students] => 1
                )

            [1] => Array
                (
                    [class] => Intermediate Hip Hop Ages 9+
                    [session] => 0
                    [start] => 1436899500
                    [end] => 1436902200
                    [capacity] => 
                    [students] => 1
                )

            [2] => Array
                (
                    [class] => Beginning Pointe Ages 10+
                    [session] => 0
                    [start] => 1436896800
                    [end] => 1436899500
                    [capacity] => 
                    [students] => 1
                )

            [3] => Array
                (
                    [class] => Int/Adv Ballet  Ages 10+
                    [session] => 0
                    [start] => 1436889600
                    [end] => 1436896800
                    [capacity] => 15
                    [students] => 1
                )

            [4] => Array
                (
                    [class] => Beginning Ballet 8+ year olds
                    [session] => 0
                    [start] => 1436884200
                    [end] => 1436891400
                    [capacity] => 15
                    [students] => 1
                )

        )

    [2] => Array
        (
            [0] => Array
                (
                    [class] => Intermediate Technique/Progressions Ages 9+
                    [session] => 0
                    [start] => 1436899500
                    [end] => 1436904900
                    [capacity] => 
                    [students] => 1
                )

            [1] => Array
                (
                    [class] => Int/Adv Tap Ages 9+
                    [session] => 0
                    [start] => 1436895900
                    [end] => 1436899500
                    [capacity] => 
                    [students] => 1
                )

            [2] => Array
                (
                    [class] => Beginning Jazz/Contemporary Technique Ages 8+
                    [session] => 0
                    [start] => 1436887800
                    [end] => 1436893200
                    [capacity] => 
                    [students] => 1
                )

        )

    [3] => Array
        (
            [0] => Array
                (
                    [class] => Int/Adv Jazz 9+
                    [session] => 0
                    [start] => 1436893200
                    [end] => 1436898600
                    [capacity] => 
                    [students] => 1
                )

            [1] => Array
                (
                    [class] => Int/Adv Ballet Barre Ages 9+
                    [session] => 0
                    [start] => 1436886000
                    [end] => 1436889600
                    [capacity] => 
                    [students] => 1
                )

        )

)

我想按照开始时间对数组的第三级（类）进行排序。我已经尝试了一些不同的解决方案，这里提出了两个级别的数组，但没有用。

我最近的尝试是：

array_walk($schedule, 'walk_cmp');

function walk_cmp($array, $key){
    usort($array, function($a, $b) { 
      return ($a['start'] > $b['start']) ? -1: 1;
    });
}

我已确认排序在walk_cmp内有效，但对数组的更改不会反映在主数组中。

我觉得我必须遗漏一些明显的东西，但我在这里。请记住，这是一个动态的示例阵列。它将始终具有此结构，但第二个（日）和第三个（类）数组中的元素数量将有所不同。

Answer 1

您的尝试看起来很好，而且您也非常接近解决方案！

您的主要问题是，您将函数中的数组排序为局部变量。所以你的原始数组不会改变。你必须传递数组by reference.所以你的代码看起来像这样：

array_walk($schedule, "walk_cmp");

function walk_cmp(&$array, $key) {
                //^ See here
    uasort($array, function($a, $b) { 
        if($a['start'] == $b['start']) //If they are the same, return 0
            return 0;
        return ($a['start'] > $b['start']) ? -1 : 1;
    });

}

Answer 2

有几种简洁现代的方法可以做到这一点：

1. array_walk()和array_multisort()和array_column()：（Demo）

   array_walk($array, function(&$v) {
       array_multisort(array_column($v, 'start'), $v);
   });
   

   这会在迭代数组的第一级时通过引用进行修改，然后根据第三级中的目标列对第二级进行排序。 array_multisort()也会通过引用进行修改。

2. array_walk()和usort()和三向比较运算符（正式命名为“太空飞船运算符”）（Demo）

   array_walk($array, function(&$a1) {
       usort($a1, function($a2, $b2) {
           return $a2['start'] <=> $b2['start'];
       });
   });
   

   从PHP7.4 起，箭头函数语法可用于减少总体语法。 （Demo）

   array_walk($array, function(&$a1) {
       usort($a1, fn($a2, $b2) => $a2['start'] <=> $b2['start']);
   });
   

   您甚至可以简化array_walk()语法以形成单线：（Demo）

   array_walk($array, fn(&$a1) => usort($a1, fn($a2, $b2) => $a2['start'] <=> $b2['start']));
   // array_walk silently ignores the data returned by the "arrow"